Cleaning up the Juanacatlan Falls, the “Niagara of Mexico”

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Jan 142016
 

Geo-Mexico has repeatedly lamented the sad state of the Juanacatlán Falls, the “Niagara of Mexico”, near Guadalajara. More than a century ago, they were considered a national treasure. Indeed, in 1899, they were among the earliest landscapes to be featured on Mexican postage stamps.

In 2012, we reported that Greenpeace demands action to clean up Mexico’s surface waters. Greenpeace activists chose to protest at the Juanacatlán Falls to call attention to the poor quality of Mexico’s rivers and lakes. The activists cited government statistics showing that 70% of Mexico’s surface water was contaminated, mostly from toxic industrial dumping, rather than municipal sewage.

Greenpeace activists at El Salto de Juanacatlán, 22 March 2012. Photo: Greenpeace.

Greenpeace activists at El Salto de Juanacatlán, 22 March 2012. Photo: Greenpeace.

Last year, we returned to the theme and looked at how the Juanacatlán Falls had been transformed from the “Niagara of Mexico” to the “Silent River”.

Our concluding paragraph on that occasion bears repeating:

Is it too much to hope that the government, corporations and society in the El Salto area can all come together to remedy this appalling tale of willful mismanagement? Local residents are right to insist on the enforcement of existing water quality regulations and on the implementation of remedial measures to reverse the decline of this major river and its once-famous waterfalls. Even more importantly, urgent measures are needed to reverse the deteriorating public health situation faced by all those living or working nearby.

Finally, some good news. Author and activist John Pint, who has done far more than most to publicize the scenic wonders of Western Mexico (including dozens of places that fall way outside the usual tourist guides) reports that the inflow from the 66-km-long Ahogado River, one of the rivers that feeds into the Santiago River just before the Juanacatlán Falls is being cleaned up, with a dramatic, positive impact on the beauty of the Falls themselves. According to Pint’s first-hand report and photographs – Is Guadalajara’s most infamous waterfall now clean? – the smelly, toxic foam that has marred the Falls for decades has become a thing of the past. While this does not mean the water is completely clean, it is certainly an encouraging start.

The Ahogado River itself continues to receive pollutants, and its water remains heavily contaminated, but a  300-million-peso treatment plant, which apparently began operations in 2012, is removing some of the worse contaminants prior to the river joining the Santiago River. There is still a lot of work to be done here if the Juanacatlán Falls are going to be restored to their former pristine beauty, but Geo-Mexico is delighted to hear that progress is (finally) being made.

What a shame that it took the death of eight-year-old Miguel Ángel López in 2008, and years of adverse effects on the health of local inhabitants, before federal and state authorities took decisive action. Later this year, Geo-Mexico hopes to revisit the Falls for the first time in twenty years to see just how much they’ve improved. Watch this space!

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The River Santiago and the Juanacatlan Falls: from the “Niagara of Mexico” to the “Silent River”

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Jun 112015
 

In summer 1987, while living in Guadalajara, I entertained a fellow UK geographer, who arrived with a long list of places he wanted to visit. Over the next few weeks, we ticked them off one by one. Near the end of his visit, he asked why I hadn’t yet taken him to see the famous Juanacatlán Falls, the “Niagara of Mexico”, despite them being in his “top ten” places to see. “OK”, I said, “let’s go!”

Traffic was heavy and as we drove across Guadalajara, I could see his impatience building. Finally, he asked me, “Where are they? How close are we?” I replied that we were “fairly close” but that I was absolutely certain that he would recognize them before they came into sight. A few minutes later and he screwed up his nose and said, “Ughh. What’s that smell?” “See?”, I said triumphantly, “I knew you’d recognize them before you saw them!”

Juanacatlán Falls in 1989. Photo: Tony Burton. All rights reserved.

Juanacatlán Falls in 1989. Photo: Tony Burton. All rights reserved.

Even thirty years ago, long before NAFTA, the Juanacatlán Falls were a sorry sight (and source of a worse smell). Since then, and since NAFTA, they have only become worse. These once-majestic falls, the first Mexican landscape on a postage stamp back in 1899, have been reduced to a trickle of foul-smelling effluent. At the start of the twentieth century, the falls provided hydro-electric power for Guadalajara and turned the wheels of a cotton and woolen mill, the ruins of which now stand to one side.

A recent piece of investigative journalism about the River Santiago, the river which created these waterfalls, makes for disturbing reading. It provides plenty of evidence that the rapid increase in factories along the river, mainly post-NAFTA, may have provided 50,000 new jobs, but has also led to worsening water quality to the point where exposure to the river presents a serious public health risk.

In “River of Death“, Steve Fisher lays bare the terrible reality faced by those living and working close to the river. This is a harrowing tale, with heart-rending testimony from several local residents. On a positive note, the related video, Fusion Investigates: Silent River (below) describes how Sofía Enciso and her family have defied death threats and are determined to confront the factories responsible, while demanding that the relevant authorities take action to enforce federal water quality regulations, and start to clean up the river.

Perhaps the most telling single statistic is that precisely zero companies were fined for failing to comply with water discharge regulations between 2005 and 2011.

In the video, the mayor of El Salto, the main town near the Juanacatlán Falls, claims that the river has become polluted in the past thirty years. I guess he must be too young to remember that they were seriously polluted long before that.

Is it too much to hope that the government, corporations and society in the El Salto area can all come together to remedy this appalling tale of willful mismanagement? Local residents are right to insist on the enforcement of existing water quality regulations and on the implementation of remedial measures to reverse the decline of this major river and its once-famous waterfalls. Even more importantly, urgent measures are needed to reverse the deteriorating public health situation faced by all those living or working nearby.

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Toxic spill in Sonora copper mine causes environmental disaster

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Sep 112014
 

A toxic spill at a copper mine in the northwestern state of Sonora is the Mexican mining sector’s worst environmental disaster in recent history.

The mine is owned by mining giant Grupo México, Mexico’s largest mining corporation and operated by its Buenavista del Cobre division. Grupo México is the third largest copper producer in the world and has a rail transport division, Ferrocarril Mexicano (Ferromex), that operates Mexico’s largest rail fleet. The Buenavista del Cobre mine, part-way through a $3.4 billion expansion plan, has some of the largest proven copper reserves in the world and is the world’s fourth largest copper mine.

The spill allowed 40,000 cubic meters of toxic copper sulfate acid to enter the Tinajas stream in the town of Cananea on 6 August 2014. Buenavista del Cobre claimed the spill was the result of an unforeseeable heavy rain storm, which triggered a rise in the level of water and copper sulfate in a holding tank being constructed at the copper mine. Grupo México has formed a team of 20 experts from the University of Arizona and Mexican universities to investigate the spill.

However, an initial report by the National Water Commission (Conagua) determined that the spill was caused by a flawed polyethylene pipe at one of the mine’s leachate tanks, together with a faulty valve at another tank. Conagua attributed the environmental disaster to negligence on the part of the company. Mexico’s federal environmental protection agency (Profepa) reported that the contaminants from the spill included copper, arsenic, aluminum, cadmium, chromium, iron, manganese and lead.

Sonora-Copper-Mine-Spill-

Credit: Jesus Ballesteros/Expreso-Cuartoscuro.com

Mexico’s Environment Secretary Juan José Guerra Abud called it the “worst natural disaster provoked by the mining industry in the modern history of Mexico,” and confirmed that the spill contaminated not only the 17.6-kilometer-long (11-mile-long) Tinajas stream, but also the River Bacanuchi (64 kilometers in length), the River Sonora (190 kilometers long) and the El Molinito reservoir which stores 15.4 million cubic meters of water.

The contamination turned the waterways orange (see image) and affected the water supply of 24,000 people in seven communities along the rivers, forcing schools to close for several weeks while environmental authorities clean up the mess. More than 300 wells were shut down. The Sonora state government has been providing millions of liters of water via trucks to residents in the affected area. It has also started a temporary employment program to reactivate the local economy. The mining company has provided 13 million liters of water and $266,000 in immediate assistance to affected communities.

Some 800 mine workers, members of Mexico’s national mining and metallurgical workers union, blockaded the mine entrances in protest at the company’s failure to prevent the spill. Workers have been fighting over contracts since a strike in 2007.

The total clean-up costs are unknown, but likely to run into tens of millions of dollars.

On 18 August, Profepa filed a criminal complaint against Buenavista del Cobre and another Grupo México unit, Minera México, for their alleged roles in the spill. Grupo México could be fined up to 3.3 million dollars if the complaint is upheld.

Sonora State Governor Guillermo Padrés Elías has announced that the seven municipalities affected by the leached copper spill are filing a civil claim for damages.

Eight years ago in the northern state of Coahuila, an explosion in a coal mine belonging to Grupo México left 65 miners trapped underground; only two bodies were ever recovered.

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Ecocide in Lake Cajititlan, Jalisco: massive fish death

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Sep 062014
 

Hundreds of thousands of dead fish have washed up on the shores of Lake Cajititlán in Jalisco in the past ten days.

Lake Cajititlán is about 9 kilometers (5.6 miles) long and 2 km wide. It is mid-way between the city of Guadalajara and Lake Chapala, Mexico’s largest natural lake. Fortunately, Lake Cajititlán does not have an outlet, so water and fish from the lake can not enter other nearby streams or lakes.

Map of Lake Chapala, Jalisco, Mexico

Map of Lake Chapala, Jalisco, Mexico. Credit: Tony Burton; all rights reserved.

According to government officials, about 3 million dead popoche chub (Algansea popoche) with a combined weight of 82 metric tons were removed from Lake Cajititlán in the latest ecocide.

Initial reports contained conflicting versions of events, with local fishermen claiming far higher losses than government officials. The currently accepted figure of 82 metric tons suggests that the fishermen’s estimate was far closer to reality than the early “official” figures.

cajititlan-ecocide

(AFP Photo / Hector Guerrero)

Local authorities at first tried to persuade residents that the die-off was part of a “natural cycle”. However, this idea was quickly dispelled by state and federal agencies who are continuing investigations to establish the precise causes of the ecocide. Their preliminary technical studies have confirmed that the die-off of fish was due to contaminated water with dissolved oxygen levels well below the limits for a healthy fish population. The contamination appears to originate from raw sewage entering the lake and the inefficient operation of the existing sewage treatment plants.

Low oxygen levels could also result from seasonal rainy season runoff washing excess fertilizers into the lake, increasing the water’s nitrogen and phosphorus loads, promoting eutrophication.

State authorities have issued an environmental emergency alert for the lake, but have consistently maintained that the event has not endangered the health of local residents.

This is the fourth fish kill affecting Lake Cajititlán in 2014. This latest ecocide is only one of several ecological disasters that have befallen Mexico in recent weeks.

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Recent progress in waste water treatment in Mexico

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Aug 252014
 

Two wastewater treatment plants have been in the news recently. The first is the $230 million Agua Prieta wastewater treatment plant, located north of Guadalajara in Jalisco, which was formally inaugurated last month. It is the first stage in a plan to restore the heavily polluted Santiago River back to health. The Santiago is the outflow from Lake Chapala and receives pollutants from the industrial zone of El Salto outside Guadalajara. The initial capacity of the Agua Prieta plant is 6,500 liters/second, almost all of which is returned to the river after treatment.

The plant was built by a consortium led by ICA subsidiary Conoisa, Atlatec, and Servicios de Agua Trident under a 20-year concession. President Enrique Peña Nieto claims on his government webpage that, “Integrated, sustainable water management is a government priority. The challenge is even greater because almost 50% of the wastewater returned to the environment does not undergo any form of treatment… The Agua Prieta Wastewater Treatment Plant in Zapopan… [will] improve the quality of life of 3.3 million inhabitants in the metropolitan area of Guadalajara… It will treat 82% of the wastewater in the area, and 100% when the complementary sewage works are completed.”

agua-prieta-wastewater-According to government figures, waste water treatment coverage at the national level is currently 50.3%, with a 2018 target of 63%. Agua Prieta has raised national coverage to 53.3%, and will boost it to 54.3% once the plant is operating at full capacity and treating 8,500 liters/second of wastewater. At the state level, Jalisco is now treating 32% of its wastewater.

The Agua Prieta plant is currently the largest of its kind in Mexico and is powered by biogas derived from the wastewater sludge. However, an even larger plant is under construction, in the state of Hidalgo in central Mexico. The Atotonilco Wastewater Treatment Plant is being built by a consortium, including Mexican construction companies ICA and IDEAL, Mitsui subsidiary Atlatec and Spanish firm Acciona Agua, that won the concession to design, build, and operate this plant for 22 years, at which point the plant will be transferred to federal ownership. Work began in 2010 and is due to be completed by 2015.

The Atotonilco Wastewater Treatment Plant will be the largest wastewater plant in Latin America and one of the largest in the world, with a biological treatment capacity of 23,000 liters/second (1.99 million m3/day). The wastewater treatment is performed by a series of conventional processes, with an additional chemical process during the rainy season. Treated waters from this plant are already being used in agriculture without any additional cleaning steps. The plant is self-sufficient in terms of energy usage, since it converts the methane offgas from the wastewater sludge into electrical energy.

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Monitoring air pollution in Guadalajara

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Jun 162014
 

Air pollution in the city of Guadalajara, the state capital of Jalisco, has worsened over the past decade, though there are some recent signs of improvement :

The Jalisco Environmental Agency now has a webpage where residents and travelers alike can now monitor Guadalajara’s air quality on an hourly basis. Readings for 10 stations are superimposed on a basemap on that page, together with links to graphs showing recent trends and other meteorological data. Tabs above the map also give a link to the current wind conditions across the city. Historical data (in Spanish) can also be accessed via the link to “Datos”.

Screenshot of Guadalajara air monitoring webpage

Screenshot of Guadalajara air monitoring webpage. Note: Two stations are shown as undergoing maintenance.

The map provides summary data in IMECAs, which stands for Índice Metropolitano de la Calidad del Aire (Metropolitan Index of Air Quality). IMECAs are a compound index combining measurements of concentrations of ozone (O3), sulphur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO) and particles smaller than 10 micrometers (PM10).

In Guadalajara, formal smog alerts are issued if average readings rise above 150 IMECAs (“Very Bad”) for more than two consecutive hours. If readings rise above 200 IMECAs (“Extremely Bad”), then “serious alerts” impose restrictions on vehicle use and may lead to the suspension of school classes.

In Guadalajara, the worst air quality tends to be in the southern and eastern sections of the city. It also tends to occur in the months of April and May, immediately before the rainy season gets underway. The webpage system gives everyone an easy way to check these assertions!

In Guadalajara, mitigation efforts are centered mainly on reducing vehicle emissions (partly by stricter emissions testing and verification, and partly by improvements to the public transport network) since they are the main source of pollution. To date, there are no plans in Guadalajara to introduce a “Day without car” program similar to that in Mexico City:

Teaching idea

Use the Jalisco Environment Agency webpage to monitor Guadalajara’s air pollution and identify any patterns or trends related to air pollution in the city. Consider suggesting one or more hypotheses, such as “Air pollution gets worse in the afternoon”, or “The level of air pollution in eastern Guadalajara is worse than in western Guadalajara”, before testing your ideas using the online data.

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Pemex works at its Clean Fuels Policy

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May 222014
 

As part of its Clean Fuels Policy, Pemex is modernizing its refineries in Ciudad Madero, Minatitlán, Salamanca, Salina Cruz and Tula.The total investment involved is 3.4 billion dollars. The plan, which will take 4 years to complete, includes the construction of new plants in several of the locations

Pemex installations in Mexico. (Adapted from Fig 15.5 of Geo-Mexico). All rights reserved.

Pemex installations in Mexico. (Adapted from Fig 15.5 of Geo-Mexico). All rights reserved.

The objective is to produce Ultra Low Sulfur diesel fuel (UBA) in the five refineries, in compliance with Mexican standards. The new technology will reduce vehicle emissions of carbon dioxide and nitrogen oxides by between 50 and 80%.

Since last September, 42,500 barrels/day of ultra low sulfur gasoline is already being produced at the Pemex refinery in Cadereyta, Nuevo León.

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Apr 282014
 

Environmental noise is everywhere in Mexico, from traffic and fiestas to garbage collection and gas delivery. For more examples, see The distinctive sounds of Mexico’s towns and cities and The Sounds of Mexico. The traffic whistles made by police are an important subset of the sounds in any Mexican town or city. They have a mini-language of their own, explored in this MexConnect article: Did you know that different traffic whistles in Mexico mean different things?

This 3 minute Youtube video is a fun introduction to some of the Sounds of Mexico City though it must be admitted that some of the sounds are far more melodious than others:

Sounds and whistles may be very useful, but exposure to environmental noise can have deleterious effects on an individual’s well-being. Research in many countries has supported legislation to limit people’s exposure to loud noise on the grounds that such exposure can seriously damage health. Working days are lost and the resulting healthcare costs are considerable.

For example, a Spanish group, The National Association Against Noise Pollution, claims that the volume of music blasting out of automobile speakers makes many of that country’s younger generation “candidates for deafness”. The Association has lobbied for “coherent and efficient” legislation to prevent this modern urban environmental problem. It wants buildings with improved sound insulation and building codes which take account of the “sound maps” of each city.

Environmental noise, even if not sufficiently loud to damage our hearing, can make communication much more difficult, not to say frustrating, and can also interfere with our concentration, increasing the likelihood of potentially dangerous situations in the workplace or on the road. Excessive noise can increase stress and provoke fatigue.

What level of noise is safe? Three factors come into play. First, how intense, or loud, the noise is. This “noise level” is relatively easy to record and is measured in decibels (dB). The second factor is how long the noise lasts – the duration of any particular noise makes a huge difference to its effects on our hearing system. This is also relatively easy to quantify. The third factor – our individual susceptibility to noise – remains extremely difficult to predict in advance, meaning that noises that prove innocuous for some members of the family may permanently damage the hearing of others.

The following list indicates the peak decibel level (dBA) of various recreational and environmental noises:

  • Normal breathing: 10
  • Average home interior: 50
  • Conversational speech: 65
  • Vacuum Cleaner: 85
  • Lawn Mower: 95
  • Video Arcade: 105
  • Car horn: 110
  • Center of Guadalajara: 110
  • Screaming child: 115
  • Chain saw: 125
  • Automobile Stereo: 125-155
  • Fireworks (at range of 3 feet or 1 meter): 162
  • Hand gun:  165

This list clearly suggests that it is unwise to spend all day mowing the lawn or vacuuming your house, let alone using a chain saw or cruising the streets with your car stereo turned up high!

The World Health Organization (WHO) currently considers that 65 decibels (65 dB) should be the maximum noise level to which people are exposed for any prolonged period of time such as a working day. It estimates that at least 120 million people worldwide, mainly city residents, are suffering from hearing problems caused by exposure to excessive noise.

Mexico’s official noise norm NOM-081-SEMARNAT-1994 was first published in 1995 and follows the WHO guidelines. By comparison, the U.S. Occupational Safety and Health Administration standards are a maximum 8 hours exposure to 90 dB, 2 hours exposure to 100 dB, 1 hour to 105 dB or 15 minutes to 115 dB.

noise-chartIn November 2013, Mexico modified the technical details attached to its noise norm, and issued a new chart (see above) showing the maximum permitted noise levels in a variety of different settings. Note that the limits apply to “fixed sources” of noise, not to the occasional passing vehicle with loud-speakers!

The new rules are welcome. As John Pint eloquently puts it in New Federal Norms list decibel limits, this legislation “gives ordinary people a chance to defend themselves from Acoustic Terrorism.”

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Nov 062013
 

Mexico City and its surrounding areas have a strict “Hoy no circula” (“Today you can’t drive” or “Day without a Car”) program. The program is intended to reduce air pollution from vehicle emissions.

Day without a car table

The graphic shows the major rules for most vehicles. With few exceptions, these rules apply to all tourist vehicles as well as Mexican-plated vehicles.

Click here for a Wikipedia article with more details of the rules, including Saturday rules and exceptions

Area subject to “Day without a Car” rules, November-2013. All rights reserved.

As of November 2013, the “Hoy no circula” program applies to the Federal District and the following 18 adjoining municipalities in the State of Mexico (see map):

  • Atizapán de Zaragoza
  • Coacalco de Berriozabal
  • Cuautitlán
  • Cuautitlán Izcalli
  • Chalco
  • Chimalhuacan
  • Chicoloapan
  • Ecatepec de Morelos
  • Huixquilucan
  • Ixtapaluca
  • La Paz
  • Naucalpan de Juárez
  • Nezahualcóyotl
  • Nicolás Romero
  • Tecámac
  • Tlalnepantla de Baz
  • Tultitlán
  • Valle de Chalco Solidaridad

No responsibility or liability is assumed for any situation arising from the information contained within this post, which is believed to be accurate at the time of writing. For more details about the growth of Mexico City, and its urban issues and management strategies, consider buying a copy of Geo-Mexico: the geography and dynamics of modern Mexico, available from all good bookstores, as well as via amazon.com or this webpage.

Aug 052013
 

A recent study published by the Clean Air Institute analyzed air pollution in 22 Latin American cities:

Six Mexican cities were included in the study: Mexico City, Guadalajara, Monterrey, Puebla, Ciudad Juárez and León. However, only limited data were available for Puebla, Cd. Juárez and León. One of the main conclusions of the study is that Mexico has about the worst urban air pollution in Latin America. It is believed to be responsible for about 15,000 deaths in Mexico each year.

The focus was on the following air pollutants:

  1. Particulate matter is divided into two measures; particles less 2.5 microns in diameter (PM2.5) and those less than 10 microns (PM10). PM2.5 pollution is extremely harmful because it penetrates deep into lungs causing inflammation and worsening heart and lung diseases. This can be fatal.
  2. Ozone is formed in the air when oxides of nitrogen and volatile organic compounds mix with intense sunlight. The very intense sunlight in Mexican cities makes them particularly prone to ozone pollution.
  3. Nitrogen dioxide (NO2) is caused by high temperature combustion of fossil fuels in vehicles, factories and power plants. It can aggravate lung diseases as well as contribute to ozone and fine particle pollution.
  4. Sulfur dioxide (SO2), which also comes from burning fossil fuels, contributes to heart and respiratory disease. Unfortunately, not all of the 22 cities had data on all four pollutants. Consequently comparisons among cities are a bit limited.

According to the study, Mexican cities had some of the worst urban particulate pollution in Latin America, significantly above WHO standards. Of the 16 cities with data, Monterrey had by far the worst PM10 pollution with 85.9 micrograms per cubic meter (ug/m3); considerably worse than the perennially dusty Lima with 62.2 ug/m3. Guadalajara came second with 70.1 ug/m3, Mexico City was 6th with 57.0 ug/m3, and León placed 11th with 39.0 ug/m3, even worse than Sao Paulo at 36.5 ug/m3. Though not in the study, Mexicali has worse PM10 pollution than Monterrey. Also Monterrey’s PM10 levels are much better than many major world cities including Cairo, Delhi, Kolkata, Beijing, Chengdu, Bangalore, Shanghai, Dacca, Jakarta, and Karachi.

Mexico City air quality in 1980 (Photo: Tony Burton)

Mexico City air quality in 1980 (Photo: Tony Burton)

Mexico did a bit better with respect to the more serious PM2.5. Of the 11 cities with data, Bogota was worst with 35.1 ug/m3 followed by Lima at 31.5ug/m3 and San Salvador and Montevideo at 28.0 ug/m3. The two Mexican cities with data, Mexico City (26.2 ug/m3) and Monterrey (25.9 ug/m3) were 6th and 8th.

Mexican cities also have some of the highest levels of ozone pollution. Of the ten cities with data, five of the six worst were Mexican cities. Guadalajara had the highest ozone pollution with 69.3 25.9 ug/m3 followed closely by León 68.9 at ug/m3. Mexico City was 4th (59.4 ug/m3); Monterrey was 5th (55.2 ug/m3); and Cd. Juárez came 6th (46.3 ug/m3), just ahead of Quito (44.1). Much better ozone levels were recorded by Sao Paulo (36.0 ug/m3), Santiago (28.8 ug/m3) and Bogota (21.1 ug/m3).

Cities in Mexico also had high levels of nitrogen dioxide. The highest levels were in Montevideo (70.0 ug/m3), but Guadalajara (57.2ug/m3), Mexico City (54.2 ug/m3) and León (45.5 ug/m3) placed 2nd, 3rd and 4th worst among the 14 cities with data. Monterrey was much better with the third lowest nitrogen oxide level (29.0 ug/m3), trailing only Lima (12.8 ug/m3) and Quito (23.3 ug/m3).

Mexican cities were also among the worst in terms of sulfur dioxide pollution. Of the 13 cities with data, León had by far the highest level with (23.4 ug/m3), followed by Medellin (16.0 ug/m3). Mexico City was 3rd worst (15.3 ug/m3); Monterrey was 4th (13.1 ug/m3); and Guadalajara was 6th (8.6 ug/m3).

In summary, the study indicates that Mexico has about the worst urban air pollution in Latin America. Fortunately, Mexico City, which used to be considered one of the most polluted cities in the world, has significantly improved its air quality in the last few decades. (see Rhoda and Burton, Geo-Mexico: The geography and dynamics of modern Mexico, p 177)

On the other hand, other major cities in Mexico have not had the same experience. The data in this study appear to suggest that among Mexico’s three biggest cities, Guadalajara has the worst air pollution followed by Mexico City and then Monterrey. (This study found insufficient data for comparisons with Puebla, Cd. Juárez and León.)

Other posts on urban air pollution: